The Astronomik UHC is THE filter for visual observing.
The Astronomik UHC (Ultra High Contrast) filter allows transmission of almost 100% of radiation from both O-III and H beta, and 96% of H-alpha.
Though the second window for the H-alpha-line is not intended for visual observing, it is important when the filter is used with an imaging camera.
All scattered light from other wavelengths, including most artificial light pollution, is filtered out. This reveals a wealth of detail when observing gas nebulae and planetary nebulae.
- Nearly 100% transmission of O-III & H-beta
- 96% transmission of H-alpha
- Blocks most artificial light pollution
- Ideal all-round deep sky filter, even for small telescopes
- Not sensitive to high humidity or ageing effects
- Excellent quality substrate
- Diffraction limited - the optical performance of your telescope will not be reduced
- Parfocal with other Astronomik filters
- 1mm Glass Thickness
- Supplied in a high-quality, long lasting, filter box
The Astronomik UHC filters’ remarkably high light transmission improves views of deep-sky-objects, even when used with smaller telescope apertures! (I.e. 2" / 50mm).
Optimised for use with telescope f-ratios f/4 to f/15.
Transmission losses and chromatic distortions, which arise with other filters, only occur with Astronomik filters when they are used with extremely bright aperture ratios 1:2 and higher!
Astronomik's UHC filters use very high quality glass and optical coatings so the telescope's native performance is not degraded.
- The horizontal axis is the Wavelength in Nanometers (nm). 400nm is deep blue, at 520nm the human eye senses green and at 600nm red. At 656nm is the famous "H-Alpha" emission line of hydrogen.
- The transmission in % is plotted on the vertical axis.
- The blue line shows the transmission of the filter.
- The most important emission lines from nebulas are shown in orange. The most important lines are from ionised Hydrogen (H-alpha and H-beta) and double ionised oxygen (OIII).
The major emission lines of artificial light pollution:
| Hg 435,8nm | Hg 546,1nm | Hg 577,0nm | Hg 578,1nm |
| Na 589,0nm | Na 589,6nm | Na 615,4nm | Na 616,1nm |
The major emission lines of nebulas:
H-β 486,1nm | OIII 495,9nm | OIII 500,7nm | H-α 656,3nm
- Visual observation (dark skies): Very good, for telescopes of all apertures and high exit pupil
- Visual observation (urban skies): Very good, for telescopes from 100 mm aperture
- Film photography: Reasonable, but very long exposure time
- CCD photography: Good, when used with an additional IR-block-filter
- DSLR photography (original): Good, colour balance shifted but contrast enhanced
- DSLR photography (astro modified): Very good, colour balance is near perfect
- DSLR photography (MC modified): Good, when used with an additional IR-block-filter
- Webcam / Video (Planets): Unsuitable
- Webcam / Video (Deep Sky): Good, if light pollution is a big problem